The long-term goal of this research is the investigation of the cellular physiology of the placental transfer of important nutrients. These investigations have been extended from original studies of amino acid transport. During the forthcoming project period they will focus on the transfer of both amino acids and calcium and investigation of the cellular and biochemical processes that may be expected to underlie their transport in the human placental trophoblast. Amino acids are utilized by the fetus for growth and catabolism and calcium for skeletal mineralization. The importance of these processes, the large quantities required by the fetus and the recognition of clinical disorders of fetal growth and neonatal calcium metabolism all point to the importance of understanding the placental transfer of these important nutrients. The strengths of this project are: (1) its use of well-characterized specific preparations, some of which were developed specifically for this project, of each of the two plasma membranes and of subcellular material from the syncytiotrophoblast; and (2) its relatively unique application to the placenta of established methods for the elucidation of cellular transport mechanisms whose utility has been proven in widely accepted reports from many laboratories studying a variety of cellular and subcellular systems. Specific aims include the investigation of calcium transport methanisms of the syncytial microvillous and basal plasma membranes and cytoplasm, the characterization of amino acid transport systems of the two plasma membranes, and the investigation of the regulation of placental cellular pathways for calcium and amino acid transfer.